The present invention relates generally to improved apparatus for a center pivot irrigation system and more particularly to improved apparatus for flushing particulate matter from the system pipeline.
Center pivot irrigation systems and equipment, such as that described in my copending application Ser. No. 778,069 filed Mar. 16, 1977, and now abandoned, generally comprises a plurality of water sprinklers mounted on a series of coupled pipe sections which, in turn, are transported on mobile tower assemblies. The pipeline, in many instances, extends over one-half mile in length, and accordingly, when the pipeline is rotated about the center pivot point on the mobile tower assemblies, the system is capable of irrigating fields approximately one mile or less in diameter. A source of water is located at the center of the field, and the water is pumped into and along the length of the connected pipe sections. As the mobile tower assemblies with the pipes supported thereon rotate, water is sprayed onto the field through sprinklers which are spaced along the length of the connected pipe sections.
Center pivot irrigation systems, as is the case with most irrigation systems, are generally utilized for irrigating arid and semi-arid fields. Water obtained from wells in such areas, however, commonly contain significant amounts of particulate matter such as sand or gravel. Over the length of the pipeline, which as previously stated, may extend for more than one-half mile, the heavier particulate matter tends to precipitate from suspension in the water and settles in the pipeline. If it is allowed to accumulate, the particulate matter reduces the water delivery capacity of the system and, in an extreme case, may completely block water flow in the pipeline. This, of course, reduces the efficiency of the irrigation system and increases costs because the system must be operational for longer periods of time to deliver the requisite amount of water to the field. Accordingly, the particulate matter should be flushed periodically from the pipeline.
One apparatus heretofore provided to flush particulate matter from the pipeline of such a system comprises a short, downwardly extending drain pipe located at the outermost end of the pipeline. In such irrigation systems, the pipeline generally extends outwardly from the center pivot point beyond the outermost mobile tower assembly. A high-powered jet nozzle or gun is located at the end of the outermost pipe section for the purpose of extending the coverage of the irrigation system. By opening the downwardly extending pipe at the end of the pipeline, the particulate matter is flushed from the pipeline by the water pumped through the system. Because the drain pipe has substantially the same water carrying capabilities of the pipeline, the water moves through the pipeline faster during flushing than when the water is released under pressure through the spray nozzles. Consequently, the sand is washed along the pipeline and flushed out of the system through the drain pipe.
Several disadvantages are inherent, however, in the foregoing system for flushing the pipeline. First, the pipeline is commonly supported about ten feet above the ground by the mobile tower assemblies. Therefore, to open the drain pipe when the system is flushed, the operator, unless he is unusually tall, must carry a ladder or other means to the site in order to reach the drain pipe and open it. Of course, this involves walking through crops with a bulky ladder or the like and may result in harm to the crop. If, on the other hand, the drain pipe is lengthened so that the operator can reach the pipe and open it while standing on the ground, taller crops such as corn may be damaged by the downwardly extending pipe when the system is operational and the pipeline is transported about the center pivot point. Considering the circumference of the circular path traced by the drain pipe at the outermost end of a one-half mile pipeline, crop loss may be significant.